1. Field of the Invention
The present invention generally relates to magnetic memory devices, and more particularly to MRAM devices, in which a magnetic tunnel junction (MTJ) device is transplanted onto a thermally-sensitive substrate.
2. Description of the Related Art
MRAMs are presently fabricated on Si for integration of magnetic tunnel junctions (MTJs) with complementary metal oxide semiconductor (CMOS) technology. MTJ devices can potentially provide nonvolatile, dense, high-performance storage elements. Lower performance applications of MTJs, such as in “smart cards”, “wearable sensors”, and the like, would require fabrication of such MTJs on flexible, thermally-sensitive substrates, such as polymers and plastics. However, the thermal budget required (e.g., between about 250 to about 400.degree. C.) during processing of the MTJ devices precludes direct fabrication on these substrate materials. That is, the processing of such devices are not compatible with the low-temperature substrates.
Additionally, present day smart cards made of plastic have one or more semiconductor chips, including memory, attached to a module embedded in the card. Having the circuit directly imprinted or bonded to the card would make them more mechanically flexible, durable and lightweight. Cost is also an important factor for low performance application. Replacement of silicon chips with cheaper methods of fabricating memory circuits on plastics would be preferred. However, prior to the invention, no such method has been provided.